Induction type alternating-current relay



CROSS REFEZZSJCE Dec. 14, 1954 w. K. SONNEMANN INDUCTION TYPEALTERNATING-CURRENT RELAY Filed Oct. 13

I Pin 11 H1 3 .W Both 7 Plug 3 4 5 6 7 8 9|O Multiples of minimumclosing cuneni.

INVENTOR n n 0 m e n n 0 S K m .m W

ATTORNEY relay of Fig.

2,697,187 Patented Dec. 14, 1954 INDUCTION TYPE ALTERNATING-CURRENTRELAY William K. Sonnemann, Roselle Park, N. J., assignor toWestinghouse Electric Corporation, East Pittsburgh, Pa., a corporationof Pennsylvania Application October 13, 1951, Serial No. 251,234 11Claims. (Cl. 317-157) This invention relates to devices responsive to analternating quantity, and it has particular relation to induction-typealternating-current relays which operate with substantial time delay.

In the prior art it has been customary to provide derelays which operatewith substantial time delay. Since time curves which have differentshapes often are desired, it has been the practice to construct relayshaving different electromagnets for This has necesdifferent styles ofrelays. Examples of prior art time curves will be found on page 117 of abook entitled Silent Sentinels published by the Westinghouse ElectricCorporation, Newark, New Jersey in 1949.

In accordance with the invention, a time delay device such as a relay isconstructed with one or more adjustments permitting a single relay to beadjusted to provide various shapes of time curves. Consequently, bysuitable adjustment of the relay, the time curve of the relay may beadjusted to conform to various standard and nonstandard shapes asdesired.

piece whereas a lagging winding surrounds one of the outer pole pieces.An electro-conductive armature is positioned adjacent the pole faces ofthe three pole pieces. These pole faces provide three time-displacedmagnetic-flux components to establish a shifting magnetic field for theelectroconductive armature. independent adjustments are magnetic pathsfollowed by two of the magnetic fiux comal-mature of the relay.

It is, therefore, an object of the invention to provide an improvedelectroresponsive time-delay device having an adjustable time curve.

It is a further object of the invention to provide an improved relayhaving an electroconductive armature and provide three time-displacedmagnetic flux components for the electroconductive armature.

It is also an object of the invention to provide a relay as defined inthe preceding paragraph wherein the magnetic paths followed by ponentsare independently adjustable.

It is a still further object of the invention to provide a relay asdefined in the preceding paragraph wherein adjustable damping isprovided for the electroconductive armature.

Other objects of the invention will be apparent from the followingdescription taken in conjunction with the accompanying drawing, inwhich:

ig. l is a view in side elevation with parts broken away and partsschematically shown of an electrical relay embodying the invention. FFigl. 2 is a view in top plan of the relay illustrated in Fig. 3 is aview in side elevation with parts schematicall y shown of anelectromagnet suitable for the relay of :ig. 1.

Fig. 4 is a vector diagram showing the relationships of certainelectrical quantities which may be present in the Fig. 5 is a graphicalrepresentation of time curves which may be obtained trom the relay ot'rig. l, and

big. 6 is a view taken along the line vlVl of Fig. 1.

Referring to the drawing, rig. l shows a relay R designed t'orenergization in accordance wllh a varlaole allernatlng quantity. "thisrelay includes a stator 1, ln Wl'llCll a shaft 3 carrying anelectroconductive armature a is mounted for rotation. Conveniently, theelectroconductive armature 5 may be in the torm of a disc constructed ofaluminum or copper.

to produce a torque urging the 018C in a predetermined direction aboutits axis.

Preferably, adjustable damping is provided for the electroconductivearmature 5. Convenlently, such damping may be provided by ahorseshoe-shaped permanent magnet 9 constructed of a high-coercivepermanent-magnet material. The permanent magnet 9 has its two pole faces(identifi d by the reference characters N for North for South pole)positioned adjacent one race non-magnetic material such as Preferably,the plug is adjustlengths or the of the magnetic field therein. the plugmay have screw threads in threaded engagement with threads provided inthe holder 11. By rotation of the plug 13, the plug may be moved towardsor away from the associated permanent magnet 9 to modify the strength ofthe magnetic field within which the electroconductive armature rotates.As well understood in the art, such rotation of the electroconductivestator to which the body or holder 11 is secured and theelectroconductive armature.

spiral control spring 15 has its inner end secured to the shaft 3 andthe stator 1.

the electromagnet 7 acting on the electroconductive armature 5, and onthe magnitude of the damping applied to the electroconductive armature 5by the damping magnet assembly. The time also may be varied by adjustingthe position of the movable contact 17 about the shaft 3. Thus, movablecontact 17 is illustrated as displaced by an angle of about the shaft 3from the fixed contact 19. If the movable contact 17 is adjusted aboutthe axis of the shaft 3 to the position illustrated in dotted lines 17A,the time required for movement of the movabie contact into the fixedcontact 19 is materially deon the shaft 3 by the spring 15 increases. Tocompensate for such increase, the disc may have a spiral periphery whichis shown in Fig. 2. It will be noted that as the movable contact 17rotates towards the fixed contact 19, the radius of the disc 5 at theelectromagnet 7 increases. Such increase in radius increases the torqueexerted on the shaft 3 by the electromagnet 7 and may be proportioned tocompensate for the increase in bias exerted by the spring 15. This meansthat if the electromagnet 7 is energized at the minimum required amountto initiate movement of the associated electroconductive armature in thedirection of the arrow 5A, the armature will continue in substantiallyuniform motion as long as the energization of the electromagnet 7remains constant until the contact 17 engages the fixed contact 19.

Referring to Fig. 3, it will be noted that the electromagnet 7 includesan E-shaped magnetic structure 21 having three pole pieces 21A, 21B and21C disposed substantially in a common plane. The magnetic structure 21may be constructed of a plurality of laminations of soft magneticmaterial, such as soft iron, each having a shape illustrated in Fig. 3.Alternatively, each of the laminations may be constructed of two or moreparts, and the parts may be associated by means of butt or interleavedjoints which are well known in the art.

The pole pieces 21A, 21B and 21C have pole faces 21a, 21b and 210 whichare disposed in a common plane, and this plane is transverse to theplane of the pole pieces 21A, 21B and 21C.

Energization for the electromagnet 7 is provided by means of a winding23 which surrounds the intermediate pole piece 213. Conveniently, thiswinding may have an adjustable number of turns as represented byadjustable tap 23A.

The winding 23 may be connected for energization in accordance with anydesired alternating quantity. For example, the winding 23 may beenergized in accordance with alternating voltage. However, it will beassumed that the winding 23 is energized through a current transformer25 in accordance with alternating current fiowing in a circuitrepresented by the conductors L1 and L2. Although the circuit may be apolyphase circuit, it will be assumed that the conductors L1 and L2represent a single-phase alternating-current circuit operating at apower frequency of 60 cycles per second.

When the winding 23 is energized, magnctomotive forces are establishedbetween the pole faces to produce a magnetic field in the area occupiedby a portion of the clectroconductive armature 5. In order to decreasethe magnetic reluctance offered to the flow of magnetic flux, a magneticmember 27 is spaced from the pole faces 21a, 21b and 210 toprovide-air-gaps between the member 27 and the pole faces. Theelectroconductive armature 5 passes through these air-gaps.

The magnetic member 27, like the magnetic structure 21, may beconstructed of soft magnetic laminations, each having a shape similar tothat illustrated in Fig. 3.

When energized, the winding 23 produces a magnetometive force whichdirects magnetic fiux components through parallel paths. One of thepaths includes the pole piece 21B, the pole piece 21A, a portion of themagnetic member 27, and the air-gaps between the magnetic member 27 andthe pole faces 21a and 21b. The second path includes the pole piece 218,the pole piece 21C, a portion of the magnetic member 27 and the air-gapsbetween the magnetic member and the pole faces 21b and 21c. Magneticflux components flowing in the pole pieces 21A, 21B and 21C arerepresented in Fig. 4 by vectors r,, em and In order to establish aphase displacement between certain of the magnetic fluxes, a closedlagging winding 29 surrounds the pole piece 21A. Although the laggingwinding may be a continuous and fixed closed winding, it will be assumedthat the winding is closed through a switch 31, and that the number ofturns in the winding are adjustable by means of a tap 33.

The lagging winding 29 produces a substantial phase displacement betweenthe magnetic flux components L and m. Since the magnetic fiux componenton represents the vector sum'of the flux components or. and 4m, it willbe understood that the three magnetic flux components may be phasedisplaced from each other as a result of the lagging winding 29.

A portion of the magnetic flux component pr. crosses the air-gap betweenthe magnetic member 27, and the pole face 210, and is represented inFig. 4 by a vector s- Another portion of the magnetic flux component4:1. flows directly between the pole pieces 21A and 213 without enteringthe electroconductive armature 5.

In an analogous manner a part of the magnetic flux component pa flowsthrough the magnetic member 27 and is represented in Fig. 4 by a vector(fie. Another portion of the magnetic fiux component 4m passes directlybetween the pole pieces 21B and 21C.

The vectors (173. and (lie are shown out of phase with L and en,respectively, because the reference direction arrows are shown inopposite directions, respectively, in Fig. 3.

Magnetic flux which flows between the magnetic member 27 and the polepiece 21B is represented in Fig. 4 by a vector of 4m.

When the lagging winding 29 is closed through the switch 31, themagnetic flux components traversing the electroconductive armature 5reach their maximum values in the same relative directions through thegaps in the order 953., b and (17c. This produces a shifting magneticfield and applies a torque between the electromagnet and theelectroconductive armature 5 which urges the armature from left to rightas viewed in Fig. 3. If the switch 31 is opened, the two parallel pathsfor magnetic flux cornponents become symmetric and no torque is appliedbetween the electromagnet and the electroconductive armature.

The switch 31 may represent the contacts of a directional relay. Ifpower flows in one direction in the associated electrical circuit, theswitch 31 is closed to permit effective energization of theelectromagnet 7. 1f the power flow is in the reverse direction, theswitch 31 is opened to prevent operation of the relay R.

If the lagging winding 29 is omitted, or if the switch 31 is opened, andif a lagging winding is applied to the pole piece 21C, reverse operationof the relay R may be obtained. For example, let it be assumed that alagging winding 35 surrounds the pole piece 21C and is closed through aswitch 37. If the switch 37 is closed, and if the switch 31 is open, theshifting magnetic field produced by energization of the winding 23 urgesthe electroconductive armature 5 from right to left as viewed in Fig. 3.Consequently, by control of the switches 31 and 37, the direction ofoperation of the relay R may be controlled. For example, assume that inFig. l, the relay has an additional fixed contact 39, and that thespring 15 when the relay is deenergized urges the movable contact 17 toa position intermediate the two fixed contacts 19 and 39. If the switch31 is closed, energization of the relay R urges the movable contacttowards the fixed contact 19. if the switch 37 is closed, the movablecontact is urged towards the fixed contact 39. It will be assumed forpresent purposes that the winding 35 is not employed, or that the switch37 is open.

in order to control the shape of the time curve of the relay R. at leastone of the two magnetic paths offered to magnetic flux produced bycurrent flowing in the winding 23 is adjustable. Preferably both of thepaths are independently adjustable. This may be effected by provision ofone or more adjustable magnetic elements for each of the paths. Thus, inFig. 3, magnetic elements may be located in the positions represented bythe reference characters A, B, A, B, A" and B. The magnetic elements maytake the form of plugs which are screw operated. For example, in Fig. lthe plug A has a large magnetic head 39 with a stud 41 projecting fromone end thereof. The stud 41 is in threaded engagement with a portion ofthe stator 1. The head 39 is constructed of soft magnetic material suchas soft iron or steel. It is located within an opening provided in themagnetic structure 21 and is slidable through the opening in response torotation of the plug. If desired, the head 39 may be spaced from thewalls of the opening by a thin-walled non-magnetic sleeve. For example,a thin plating of non-magnetic material such as copper, may be appliedto the head 39 for this purpose.

It will be noted that each of the plugs, for example the plug B, variesthe series magnetic reluctance of the magnetic path with which it isassociated. The port-ion of the magnetic structure adjacent the plug Bcarries the entire magnetic flux em. The magnetic member 27 adjacent theposition B" carries only a portion of the magnetic flux represented bythe vector en. It will be recalled that a portion of this magnetic fluxflows directly between the pole pieces 21B and 21C without entering themagnetic member 27. Consequently, the magnetic plug in the position B"is effective only for the portion of the magnetic flux componentrepresented b the vector m.

If the magnetic plug is in the position represented by the referencecharacter 8, it controls the amount of magnetic flux shunted away fromthe electroconductive armature 5. Some magnetic flux passes between thetips of the pole pieces 21B and 21C which are relatively close as shownin Fig. 3. The magnetic plug in the position B adjustably bridges theair-gap between the tips to increase the amount of magnetic fiux shuntedaway from the armature 5. Similar comments apply to the positions A, Aand A" for plugs associated with the remaining magnetic paths.

In a preferred embodiment of the invention, the plugs A and B areemployed only in the positions shown in full lines in Fig. 3. It will beunderstood that the openings provided in the magnetic structure 21 toreceive the plugs leave bridges A1, A2, B1 and B2 which saturate for lowvalues of magnetic flux therethrough. When the plugs A and B areintroduced into their associated openings, they shunt magnetic fluxaround their associated bridges and thus alter the magnetic reluctancesof the paths which contain the plugs.

Although unnecessary for an understanding of the invention, it may behelpful to consider my present understanding of the vector relationshipsexisting in the relay of Fig. 2. The windings 23 and 29, together withassociated parts of the magnetic structure, correspond somewhat to atransformer having a short-circuited secondary winding. Let it beassumed that a current represented by a vector I: (Fig. 4) flows in thewinding 29. A voltage Vz must be induced in the winding to produce thedesired flow of current. In Fig. 4 the current I: is illustratedslightly lagging the voltage V2.

To induce the voltage V2, a flux 4m is required, and this is shownlagging the voltage V2 by 90. The amount of current in the winding 23required to produce a flux L is represented in Fig. 4 by the current I3.Inasmuch as the magnetic core for the windings 23 and 29 has substantialair-gaps therein, it will be assumed that the current I3 issubstantially in phase with the magnetic flux r..

The vector sum of the currents I2 and I3 represents the current It whichflows in the winding 23. The magnetomotive force produced by the currentI flowing through the winding 23 also produces a flux me which flowsthrough the pole piece 21C. The flux n is shown in phase with thecurrent I1 in Fig. 4. The vector sum of the magnetic fluxes R and r.represents the magnetic flux em flowing in the pole piece 218.

As previously pointed out, part of the magnetic fiux M does not passthrough the magnetic member 27. Consequently, the portion b which passesthrough the magnetic member 27 is illustrated in Fig. 4 with a somewhatsmaller magnitude. For the assumed conditions, the vectors 45a. and 4mare shown 180 displaced respectively from the fluxes 451, and n andsomewhat smaller in magnitude. From a consideration of Fig. 4, it willbe noted that the phase order of the air-gap magnetic fluxes is 453.,

gas and m. This produces a shifting magnetic field and effects thedesired rotation of the electroconductive armature 5.

The effect of the plugs A and B on the performance of the relay may beconsidered with particular reference to Fig. 5. In Fig. 5 ordinatesrepresent the time in seconds required for the movable contact 17 tomove into engagement with the fixed contact 19 after the application tothe relay of an energizing element. Abscissa in Fig. 5 representmultiples of the minimum current required to effect engagement of thecontacts 17 and 19.

It the plug A is completely out of the magnetic structure 21, and if theplug B is completely inserted in the magnetic structure, a time curve Iis obtained. If both of the plugs A and B are completely out of themagnetic structure, a time curve II is obtained. If the plug A is partlyout of the magnetic structure, whereas the plug B is completely in themagnetic structure, the time curve III is obtained. If both of the plugsA and B are completely in the magnetic structure, the relay has the timecurve IV. If the plug A is completely in the magnetic structure and theplug B is completely out of the magnetic structure, the relay has a timecurve V. Intermediate positions of the plugs have intermediate effectson the shape of the time curve.

It will be noted that the plugs A and B do not have 6 similar eifects onthe shape of the time curve. Thus, removal of the plug A results in thecurve I which differs appreciably from the curve V obtained when theplug B is removed from the magnetic structure. Because of the differencein the effect of the two plugs on the time curve, the shape of the timecurve may be completely controlled over a wide range of variation.

In the preferred embodiment of the invention, the time curves allapproach a common point. For example, in the embodiment illustrated inFig. 5, all of the curves approach a point at which the relay, whenenergized with twice minimum closing current, requires 27 seconds forthe contacts to close. The position of this common point is controlledby adjustment of the damping magnet assembly. This is for the reasonthat the bridges A1, A2, B1 and B2 of Fig. 3 do not saturate at the lowenergization represented by twice minimum closing current. For thisreason the common point is substantially independent of the adjustmentof the plugs A and B. For larger energizations of the relay, the bridgesalone are unable to carry the entire magnetic flux without saturating.For this reason, the plugs A and B have substantial effects on the shapeof the time curve.

Although the invention has been described with reference to certainspecific embodiments thereof, numerous modifications falling within thespirit and scope of the invention are possible.

I claim as my invention:

1. In an electrical time-delay relay device responsive to an alternatingquantity, a magnetic structure having first, second and third spacedpole pieces, a winding surrounding the first pole piece and effectivewhen energized for directing magnetic flux in parallel through thesecond and third pole pieces, an electroconductive member mounted formovement relative to the magnetic-structure, said pole pieces havingpole faces adjacent the electroconductive member for directing theretomagnetic flux having components substantially transverse to theelectroconductive member, closed-circuit electroconductive meansassociated with the second pole piece for continuously altering the timephase of magnetic flux passing therethrough by a predetermined amountwhen the winding alone is energized to produce a shifting magnetic fieldfor the electroconductive member, said electroconductive member beingmounted for rotation relative to the magnetic structure, in combinationwith adjustable damping means for opposing rotation of theelectroconductive member by an adjustable force which varies as afunction of the rate of rotation of the electroconductive member, andmeans for varying the magnetic path for magnetic flux traversing thesecond pole piece independently of the magnet path for magnetic fluxtraversing the third pole piece.

2. In an electrical induction relay device responsive to an alternatingquantity, a magnetic structure comprising first, second and third polepieces having pole faces disposed substantially in alignment in a commonplane, a magnetic member spaced from said pole faces to define anair-gap between the member and each of the pole faces to reduce themagnetic reluctance offered to magnetic flux produced by magnetomotiveforces across said pole faces, an electroconductive armature mounted forrotation relative to the magnetic structure about an axis, saidelectroconductive armature having a portion spaced from the axis andpositioned for movement through the air-gap, a winding surrounding thefirst pole piece, the intermediate one of said pole faces being on thefirst pole piece, said magnetic structure being effective for directingmagnetic flux produced by the winding when energized through the secondand third pole pieces in parallel paths, a closed-circuit lagging coillinked with the magnetic flux traversing the second pole piece toproduce a shifting magnetic field in the air-gap having componentsentering a surface of the armature in directions substantiallytransverse to the surface when the winding is energized by alternatingcurrent, said lagging coil being closed through a circuit independent ofthe position of the electroconductive armature, damping means foropposing rotation of the electroconductive member with a force whichvaries as a function of the rate of rotation of the armature; andadjusting means for varying the magnetic path for magnetic fluxtraversing one of said parallel paths independently of the other of saidparallel paths.

3. A device as claimed in claim 2 wherein a first magnetic fluxcomponent produced by energization of the winding traverses a firstmagnetic path which includes in series the first pole piece, the secondpole piece, a portion of the magnetic member and the air-gaps betweenthe magnetic member and the first and second polefaces, and wherein asecond magnetic flux component produced by energization of the Windingtraverses a second magnetic path which includes the first pole piece,the third pole piece, a portion of the magnetic member and the air-gapsbetween the magnetic member and the first and third polefaces, andwherein said adjusting means comprises a variable magnetic sectionlocated in one of said magnetic paths.

4. A device as claimed in claim 3 wherein the ad justing means comprisesa separate magnetic element located in each of said magnetic paths, eachof the magnetic elements being independently adjustable relative to themagnetic structure for varying the eifective crosssection of theassociated magnetic path.

5. In an induction time-delay relay, an electromagnet having an airgapand having means effective when energized for producing magnetic fluxcreating a shifting magnetic field in the airgap, an electroconductivearmature mounted for rotation relative to the electromagnet and having aportion spaced from the axis of rotation positioned in the airgap, saidportion being positioned substantially transversely relative to at leasta part of the magnetic flux of said magnetic field biasing means forbiasing the armature towards a predetermined position relative to theelectromagnet with a torque which varies as the armature rotatesrelative to the electromagnet, said armature having a configurationpresenting a varying effective portion to said airgap as the armaturerotates to compensate substantially for the variation in the biasexerted by said biasing means, adjustable damping means for dampingrotation of the armature relative to the electromagnet, and adjustingmechanism adjustable for varying the shape of the curve representing theratio of energization applied to the electromagnet relative to the timerequired for the armature to rotate through a predetermined angulardistance over a substantial range of the magnitude of the energizationapplied to the electromagnet said adjusting mechanism comprising amanually-adjustable device for adjusting the magnetic path offered tomagnetic flux producing said shifting magnetic field.

6. In an induction time-delay relay, an electromagnet having an airgapand having means effective when energized for producing magnetic fiuxcreating a shifting magnetic field in the airgap, an electroconductivearmature mounted for rotation relative to the electromagnet and having aportion spaced from the axis of rotation positioned in the airgap, saidportion being p sitioned substantially transversely relative to at leasta part of the magnetic fiux of said magnetic field biasing means forbiasing the armature towards a predetermined position relative to theelectromagnet with a torque which varies as the armature rotatesrelative to the electromagnet, said armature having a configurationpresenting a varying eifective portion to said airgap as the armaturerotates to compensate substantially for the variation in the biasexerted by said biasing means, damping means for damping rotation of thearmature relative to the electromagnet with a force dependent on therate of rotation of the armature, said electromagnet comprising a firstwinding, a first magnetic path for directing a first magnetic fluxproduced by the first winding when energized by alternating current intothe airgap, a second magnetic path for directing a second magnetic fluxproduced by the first winding when energized into the airgap, a closed\"inding linked with the first magnetic path for lagging magnetic fluxtraversing the first path to alter the phase r iationship between thefirst and second magnetic fluxes, one of said magnetic paths having aportion which saturates in the range of energization of theelectromagnet to an extent dependent on the magnitude of suchenergization, and adjustable mechanism for adjustably decreasing themagnetic reluctance of said portion of the last-named magnetic path tovary the shape of the curve representing the ratio of energizationapplied to the electromagnet relative to the time required for thearmature to rotate through a predetermind angular distance.

7. In an induction time-delay relay, an electromagnet having an airgapand having means effective when energized for producing magnetic fluxcreating a shifting magnetic field in the airgap, an electroconductivearmature mounted for rotation relative to the electromagnet and having aportion spaced from the axis of rotation positioned in the airgap, saidportion being positioned substantially transversely relative to at leasta part of the magnetic flux of said magnetic field biasing means forbiasing the armature towards a predetermined position relative to theelectromagnet with a torque which varies as the armature rotatesrelative to the electromagnet, said armature having a configurationpresenting a varying etfective portion to said airgap as the armaturerotates to compensate substantially for the variation in the biasexerted by said biasing means, permanent magnet damping meansestablishing a damping magnetic field for the armature, saidelectromagnet comprising a first winding, a first magnetic path fordirecting a first magnetic fiux produced by the first winding whenenergized by alternating current into the airgap, a second magnetic pathfor directing a second magnetic flux produced by the first winding whenenergized into the airgap, a closed winding linked with the firstmagnetic path for lagging magnetic flux traversing the first path toalter the phase relationship between the first and second magneticfluxes, each of said magnetic paths having a portion which saturates inthe range of energization of the electromagnet to an extent dependent onthe magnitude of such energization, adjusting mechanism for adjustablydecreasing the magnetic reluctance of each of said portions of thelast-named magnetic path, and adjustable damping means for dampingrotation of the armature relative to the electromagnet, said adjustingmechanism being adjustable for varying the shape of the curverepresenting the ratio of energization applied to the electromagnetrelative to the time required for the armature to rotate through apredetermined angular distance over a substantial range of the magnitudeof the energization applied to the electromagnet.

8. In an induction time-delay relay, an electromagnet having an airgapand having means etfective when energized for producing magnetic fluxcreating a shifting magnetic field in the airgap, an electroconductivearmature mounted for rotation relative to the electromagnet and having aportion spaced from the axis of rotation positioned in the airgap, saidportion being positioned substantially transversely relative to at leasta part of the magnetic flux of said magnetic field biasing means forbiasing the armature towards a predetermined position relative to theelectromagnet with a torque which varies as the armature rotatesrelative to the electromagnet, said armature having a configurationpresenting a varying effective portion to said airgap as the armaturerotates to compensate substantially for the variation in the biasexerted by said biasing means, circuit-controlling means responsive to apredetermined rotation of the armature, said electromagnet comprising afirst winding, a first magnetic path for directing a first magnetic fluxproduced by the first winding when energized by alternating current intothe airgap, a second magnetic path for directing a second magnetic fiuxproduced by the first winding when energized into the airgap, a firstlagging winding linked with the first magnetic path, means for closingthe lagging winding through a circuit independent of the position of thearmature, a second lagging winding linked with the second magnetic path.means for closing the second lagging winding through a circuitindependent of the position of the armature, and manually-operable meansfor adjusting the magnetic reluctance of at least one of said magneticpaths.

9. In an induction time-delay relay, an electromagnet having an airgapand having means effective when energized for producing magnetic fluxcreating a sihfting magnetic field in the airgap, a current transformerhaving a secondary winding connected for energizing said means, anelectroconductive armature mounted for. rotation relative to theelectromagnet and having a portion spaced from the axis of rotationpositioned in the airgap, biasing means for biasing the armature towardsa predetermined position relative to the electromagnet with a torquewhich varies as the armature rotates relative to the electromagnet, saidarmature having a configuration presenting a varying effective portionto said airgap-as the armature rotates to compensate substantially forthe variation in the bias exerted by said biasing means,circuit-controlling means responsive to a predetermined rotation of thearmature, damping magnet means tor damping IOtiitiOIl of the armaturerelative to the eiectromagnet \.ith a force dependent on the rate orrotation or the armature, said eiectromagnet comprising a first winding,a first magnetic path for directing a rim magnetic hux produced by thefirst Winding when energized by alternating current into the airgap, asecond magnetic path for directing a second magnetic flux produced bythe first winding when energized into the airgap, a closed windinglinked with the first magnetic path for lagging magnetic flux traversingthe first path to alter the phase relationship between first and secondmagnetic fluxes, means for adjusting the lagging efiect of said laggingwinding, and adjusting mechanism for adjusting the magnetic reluctanceoffered by one of the magnetic paths to the associated magnetic flux tovary the shape of the curve representing the ratio of energizationapplied to the electromagnet relative to the time required for thearmature to rotate through a predetermined angular distance.

10. An alternating-current, electro-responsive, adjustable-time-delayrelay wherein contacts are operated to control an electrical circuit,the combination with said contacts of contact operating relay meanscomprising a three-pole electromagnet field-element having a yoke pieceand three projecting pole pieces disposed substantially in a commonplane, an electroconductive contact-operating armature disc, meansmounting the armature disc for rotation about its axis relative to theelectromagnet field-element, biasing means for biasing the armature discrelative to the field-element about the axis in a predetermineddirection, said pole pieces having pole faces disposed substantially ina common plane substantially parallel to and spaced by an air gap from aportion of a first face of the armature disc spaced from the axis,alternating-current exciting winding means disposed on the central oneof said pole pieces for producing magnetic flux in the central polepiece, the outer pole pieces and the two halves of the yoke piececonstituting first and second parallel return-flux paths for the centerpole piece magnetic flux, closed winding means on one of said outer polepieces for lagging magnetic flux passing therethrough to establish whenthe exciting means is excited a torque urging the armature disc againstsaid biasing, a permanent magnet assembly establishing a magnetic fieldfor a portion of the armature disc for damping rotation of the armaturedisc, and a pair of independently operable adjusting mechanisms eachoperable for adjusting the effective magnetic cross-section of a portionof each of the returnflux paths, whereby each of the adjustingmechanisms may be operated to vary the relationship between the timerequired for the armature disc to make a predetermined rotation againstsaid biasing and the magnitude of the excitation of said excitingwinding means.

11. An alternating-current, electro-responsive, ad-

justable-time-delay relay wherein contacts are operated to control anelectrical circuit, the combination with said contacts ofcontact-operating relay means comprising a three-pole electrotnagnetfield-element having a yoke piece and three projecting pole piecesdisposed substantially in a common plane, an electroconductivecontact-operating armature disc, means mounting the armature disc forrotation about its axis relative to the electromagnet field-element,biasing means for biasing the armature disc relative to thefield-element about the axis in a predetermined direction, said polepieces having pole faces disposed substantially in a common planesubstantially parallel to and spaced by an air gap from a portion of afirst face of the armature disc spaced from the axis,alternating-current exciting winding means disposed on the central oneof said pole pieces for producing magnetic flux in the central polepiece, a magnetic structure spaced by an air gap from a second face ofthe armature disc providing two halves for respectively guiding magneticflux traversing said armature disc between the central pole piece andeach of the outer pole pieces, the outer pole pieces, the two halves ofthe magnetic structure, and the two halves of the yoke piececonstituting first and second parallel return-flux paths for the centerpole piece magnetic flux, closed winding means on one of said outer polepieces for lagging magnetic flux passing therethrough to establish whenthe exciting means is excited a torque urging the armature disc againstsaid biasing, an adjustable permanent magnet assembly establishing anadjustable magnetic field for a portion of the armature disc for dampingrotation of thearmature disc, and a pair of independently operableadjusting mechanisms each operable for adjusting the efiective magneticcross-section of a portion of each of the return-flux paths, wherebveach of the adjusting mechanisms may be operated to vary therelationship between the time required for the armature disc to make apredetermined rotation against said biasing and the magnitude of theexcitation of said exciting winding means, said adjusting mechanismsbeing operated to provide different cross sections for said return-fluxpaths.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,354,142 Smith Sept. 28, 1920 2,110,313 Warrick Mar. 8, 19382,282,986 Wood May 12, 1942 2,419,396 Frisk Apr. 22, 1947 2,488,443Sonnemann Nov. 15, 1949 FOREIGN PATENTS Number Country Date 174,218Germany Dec. 23, 1904 337,119 Great Britain Oct. 30, 1930 550,795 FranceMar. 20, 1923

